PEP 681: Remove hash alias for unsafe_hash

[debonte]

@davidfstr pointed out that having a hash alias for unsafe_hash is disguising a potentially unsafe feature as safe.

We don't remember why we added a hash alias. It may have been a mistake. Or it may have been added because attrs uses hash instead of unsafe_hash. However, the attrs documentation recommends against setting hash, so this should be unusual. Attrs can add an unsafe_hash alias on their side if needed.

cc: @hynek

[hynek]

I understand that the field argument is not relevant to this PEP, but it seems like this PEP is kind of enforcing to have a inconsistent naming between decorator (unsafe_hash) and field (hash)?

[CAM-Gerlach]

@hynek You might want to bring this up on the PEP's discussion thread

[debonte]

inconsistent naming between decorator (unsafe_hash) and field (hash)?

@hynek, I don't see this as an inconsistency. The hash field parameter determines whether the field will be included in hash calculations if a __hash__ method is generated. A __hash__ method can be generated without explicitly setting unsafe_hash, for example when "eq and frozen are both True" (quoted from PEP 557). The word "unsafe" in the name of unsafe_hash is a warning that setting the value explicitly is not recommended. However, setting the hash property on fields is safe.

[hynek]

The was my first thought too, so I checked the dataclasses docs and it says:

hash: This can be a bool or None. If true, this field is included in the generated hash() method. If None (the default), use the value of compare: this would normally be the expected behavior. A field should be considered in the hash if it’s used for comparisons. Setting this value to anything other than None is discouraged.

The discouraged part makes it weird to me to have one argument have a different name than the overarching one.

Anyhow it’s not that I super care about it, it just sprung into my eye while looking at related attrs code. I’m currently sick though on a phone, so I have no time to work on this in any way (including PEP threads).

I try to add the alias for the next release.